Abstract
The systematization of processes responsible for the incorporation of trace elements in real crystals of minerals led to understanding of the role of such fairly common geochemical phenomena as endocrypy, sorption, and the origin of nonautonomous phases [1]. An experimental study conducted with trace elements and with regard for these phenomena and processes requires the application not only of modern complicated analytical techniques but also new technologies of experimental‐analytical studies. One of the elements of this technology may be the analysis of statistical samplings of analytical data on single crystals. The proposed approach is underlain by the postulate that, at a large enough number of homogeneous determinations (i.e., analyses of single crystals of similar composition by the same method), the number of the modes in which an element can occur roughly corresponds to the number of modes in the distribution of the concentration of this element. The rigorous solution of this problem can be accomplished with the use of statistically representative material. Then one can construct a diagram for the distribution frequency of the concentrations and determine the number of the distribution modes. In a real situation, the researcher usually has to constrain himself to considering approximately 20 determinations, which enables him to justify the modes only with significant contrasts. There are good reasons to believe that gold and other noble metals are contained, in a general case, in at least three modes, which are contrasting enough to be distinguished by statistical methods. It is well known that Au, Pt, and other noble metals can be adsorbed from solutions by mineral adsorbents via sorption, chemosorption, and the reduction of ions to the elemental state [2]. Moreover, these elements may be contained (although in insignificant concentrations) in the structures of various minerals. The corresponding modes of occurrence are structural admixtures (on the scale of atoms or small defects in crystals, a homogeneous distribution), adsorbed admixtures (molecular complexes or nonautonomous phases, the distributions may be either homogeneous or heterogeneous), and inclusions of autonomous phases (predominantly particles of native metal of various size, all of them much larger than the sizes of atoms, heterogeneous distributions). In order to subdivide a set X i of analytical data according to the occurrence modes of a trace element, one should consider the properties of each of the modes. These properties predetermine (among other things) the conditions of X i transition between the levels, which are identified with a set of the concentrations of the element in a certain mode of its occurrence. Technologically, the essence of this approach is the successive “screening” of a large enough representative sampling of analytical data on single crystals (monocrystals) in order to determine the whole concentrations of the element corresponding to certain modes in which the element occurs in the crystals.
Published Version
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